upward and forward until they are blended with the tubercles of the
_corpora quadrigemina_. The second are the _crura cerebelli_, which
unite in two large _fasciculi_, or pyramids, and are finally lost in the
_pons varolii_. The inferior peduncles are the corpora restiformia,
previously described, and consist of both sensory and motor filaments.
Some physiologists suppose that the cerebellum is the source of that
harmony or associative power which co-ordinates all voluntary movements,
and effects that delicate adjustment of cause to effect, displayed in
muscular action. This fact may be proved by removing the cerebellum of a
bird and observing the results, which are an uncertainty in all its
movements, and difficulty in standing, walking, or flying, the bird
being unable to direct its course. In the animal kingdom we find an
apparent correspondence between the size of the cerebellum and the
variety and extent of the movements of the animal. Instances are cited,
however, in which no such proportion exists, and so the matter is open
to controversy. The general function of the cerebellum, therefore,
cannot be explained, but the latest experiments in physiological and
anatomical science seem to favor the theory that it is in some way
connected with the harmony of the movements. This co-ordination, by
which the adjustment of voluntary motion is supposed to be effected, is
not in reality a _faculty_ having its seat in the brain substance, but
is the harmonious action of many forces through the cerebellum.

The _Cerebrum_ occupies five times the space of all the other portions
of the brain together. It is of an ovoid form, and becomes larger as it
approaches the posterior region of the skull. A longitudinal fissure
covered by the dura mater separates the cerebrum into two hemispheres,
which are connected at the base of the fissure, by a broad medullary
band, termed the _corpus callosum_. Each hemisphere is subdivided into
three lobes. The anterior gives form to the forehead, the middle rests